11.1. What is a snapshot?

A snapshot represents a frozen image of a volume.
The source of a snapshot is
called an "original."
When a snapshot is created, it looks exactly like the original
at that point in time.
As changes are made to the original, the snapshot remains the
same and looks exactly like the original at the time the snapshot was
created.

Snapshotting allows you to keep a volume online while a backup is created.
This method is much more convenient than a data backup where a volume
must be taken offline to perform a consistent backup.
When snapshotting, a snapshot of the volume is created and the backup
is taken from the snapshot, while the original remains in active use.